Study on the synthesis and characterization of polystyrene/na-mmt nanocomposites via emulsion polymerization

Abstract

Polystyrene/Na-MMT nanocomposites were prepared via emulsion polymerization. Without organically modified clay, the exfoliated nanocomposites were obtained up to 3 wt % of clay using a reactive surfactant, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), which made the polymer end-tethered on pristine Na-MMT. After the first stage polymerization was completed, dodecylbenzenesulfonic acid sodium salt (DBS-Na) was added as a particle stabilizer to obtain high conversion and exfoliate the silicate layers. The feed rate of monomers also had an effect on polymerization, and it was a key to control total monomer concentration and maintain a certain polymerization rate inside the clay. As the amount of AMPS increased, it was easy to enlarge and exfoliate the clay layers. The clay dispersion was confirmed by both X-ray diffraction and transmission electron microscopy. The synthesized nanocomposites showed the higher decomposition temperature and the higher storage modulus (E´) than pure polystyrene. In order to increase the exfoliated clay content, we synthesized the core-shell structured poly(methyl methacrylate-co-styrene)/silicate nanocomposites in which the exfoliated pristine Na-MMT silicates were well dispersed. The morphology and the mechanical properties of the P(MMA-co-ST)/silicate nanocomposites with PMMA core and PS shell, weight fraction of PMMA/PS=1/1 were studied.